[jmessner]

It seems as though the stiffer the shaft the less forward bend the shaft would have at impact with Swinging. If this is the case why wouldn't the Swinger always use the stiffest shaft possible to allow the Hinge Action control the club face more accurately?

As already suggested, I'm no TGM expert on the differences between swinging and hitting but I can give you my view on shaft flex. In general, it takes a faster swingspeed to bend a stiffer shaft a given amount, and shaft bending significantly contributes to the feel of the shaft. So if the golfer can't really bend a shaft it feels harsh, like a pipe, and it might be harder to "feel" the head through your hands during the swing. For some golfers, the feel is important and if the feel isn't just right it throws them off. It also might be harder to square up the face somewhat with less bending and you'll also likely get a lower launch angle. The general rule of thumb is that you'll get a little more control with a stiffer shaft (assuming the golfer swings the same which is a big question if the feel is poor) but better trajectory (maybe distance too) and more solid feel with a more flexible shaft. It is recommended to always go with the more flexible shaft if there is any question.

Hopefully, some experts will weigh in on the application to swingers...